Disposable diaper

ABSTRACT

A disposable diaper has a plate-like member which is and flexible and substantially non-stretchable and attached to an end flap in a rear waist region and extends in a transverse direction of the diaper. The plate-like member has stiffness higher than that of the end flap so that shrinkage and/or distortion of the end flap can be restrained by the plate-like member.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a disposable diaper utilized for toabsorption and containment of excretion discharged thereon.

[0002] An open-type disposable diaper is generally well known whichcomprises a liquid-pervious topsheet, a liquid-impervious backsheet anda liquid-absorbent core disposed between these sheets so as to define afront waist region, a rear waist region and a crotch region extendingbetween these waist regions. A pair of end flaps extend outward in thelongitudinal direction from longitudinally opposite ends of the corelying in the front and rear waist regions.

[0003] An elastic member associated with a waist-opening beingstretchable in a transverse direction is attached under tension to theend flap at least in the rear waist region. Elastic members associatedwith leg-openings being stretchable there along are attached undertension to the respective side flaps. The core comprises a mixture offluff pulp, high absorbent polymer particles and thermoplastic syntheticresin fibers compressed to a desired thickness. With such anarrangement, the core has stiffness higher than that of the top- andbacksheets. Such a diaper is well known, for example, from JapanesePatent Application Publications Nos. 1996-154973A, 1996-317950A and1996-322876A.

[0004] The end flaps usually have stiffness lower than that in theregion of the diaper containing the core, so the contraction of theelastic member associated with the waist-opening may cause a pluralityof wrinkles to be formed over substantially entire regions of the endflaps and/or the movement of the diaper wearer's body may distort theend flaps which are, in turn, partially formed with wrinkles. Theportions of the end flaps formed with wrinkles are apt to be spaced apart from the wearer s skin. Thus a undesirable clearance is generatedbetween the wearer's skin and such portions of the end flaps formed withwrinkles may cause excretion to leak through this clearance to theoutside of the diaper.

SUMMARY OF THE INVENTION

[0005] This invention aims to provide a disposable diaper improved sothat an end flap is well resistant to shrinkage and there is no anxietythat a clearance might be generated between a wearer's skin and the endflap.

[0006] According to this invention, there is provided a disposablediaper comprising a liquid-pervious topsheet, a liquid-imperviousbacksheet and a liquid-absorbent core disposed between these sheets soas to define, a front waist region, a rear waist region and a crotchregion extending between these waist regions, and a pair of end flapsextending outward in a longitudinal direction of the diaper fromlongitudinally opposite ends of the core lying in the front and rearwaist regions.

[0007] The disposable diaper further comprises a plate-like member whichis flexible and substantially non-stretchable and attached to an endflap at least in a rear waist region to extend in a transverse directionand has stiffness higher than that of the end flap.

[0008] According to one preferred embodiment of this invention, anelastic member associated with a waist-opening being stretchable in thetransverse direction is secured under tension to the end flap at leastin the rear waist region and the plate-like member lies between the endof the core and the elastic member associated with the waist-opening.

[0009] According to another preferred embodiment of this invention, theplate-like member has transversely opposite side portions and anintermediate portion extending between the transversely opposite sideportions and wherein inner surface of the plate-like member facing awearer's skin curves from the transversely opposite side portions towardthe intermediate portion so as to describe circular arcs going far offfrom the wearer's skin.

[0010] According to still another preferred embodiment of thisinvention, the intermediate portion of the plate-like member is formedto be convex toward the wearer's skin.

[0011] According to further another preferred embodiment of thisinvention, the plate-like member is made of foamable polyethylene andhas stiffness of about 0.5 mN·cm˜150 mN·cm as measured by the GurleyStiffness Test.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a plan view showing a partially cutaway diaper from theside of topsheet;

[0013]FIG. 2 is a perspective view showing the partially cutaway diaperhaving its front and rear waist regions connected to each other to beput on a wearer's body;

[0014]FIG. 3 is a sectional view taken along a line A-A in FIG. 1;

[0015]FIG. 4 is a sectional view taken along a line B-B in FIG. 2;

[0016]FIG. 5 is a sectional view taken along a line C-C in FIG. 2;

[0017]FIG. 6 is a view similar to FIG. 1 showing the partially cutawaydiaper according to an alternative embodiment of this invention; and

[0018]FIG. 7 is a sectional view taken along a line D-D in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Details of a disposable diaper according to this invention willbe more fully understood from the description of open-type diaper givenhereunder with reference to the accompanying drawings.

[0020]FIG. 1 is a plan view showing an opened and partially cutawaydiaper 1A from a topsheet 2, FIG. 2 is a perspective view showing thepartially cutaway diaper 1A which is assembled to be put on a wearer'sbody and FIG. 3 is a sectional view taken along a line A-A in FIG. 1. InFIG. 1, a longitudinal direction is indicated by an arrow Y and atransverse direction is indicated by an arrow X. It should be understoodwith respect to description of a plate-like member 6 given hereinafterthat its surface facing the wearer's skin will be referred to as aninner surface 6 a and its surface not facing the wearer's skin will bereferred to as an outer surface 6 b.

[0021] The diaper 1A basically comprises a liquid-pervious topsheet 2, aliquid-impervious backsheet 3 which comprises, in turn, a compositesheet composed of a plastic film 3 d laminated with a hydrophobicfibrous nonwoven fabric 3 c, and a liquid-absorbent core 4 disposedbetween the top- and backsheets 2, 3 and entirely covered with adiffusion sheet 5 such as tissue paper. The core 4 is joined to the top-and backsheets 2, 3 with the diffusion sheet 5 therebetween. The diaper1A further comprises a plate-like member 6 which is flexible andsubstantially non-stretchable and substantially liquid-imperviousleak-barrier cuffs 7.

[0022] The diaper 1A has the front waist region 20, the rear waistregion 22 and the crotch region 21 extending between these front andrear waist regions 20, 22. A pair of end flaps 8 extend outward in thelongitudinal direction from longitudinally opposite ends 4 a of the core4 lying in the front and rear waist regions 20, 22, respectively and apair of side flaps 9 extend outward in the transverse direction fromtransversely opposite side edges 4 b of the core 4. In the crotch region21, the side flaps 9 curve inwardly of the diaper 1A in the transversedirection so as to describe circular arcs, respectively. Each of the endflaps 8 is formed by longitudinally opposite end portions 2 a, 3 a ofthe topsheet 2 and the backsheet 3 and each of the side flaps 9 istransversely opposite side edge portions 2 b, 3 b of the top- andbacksheets 2, 3 and outermost side portions of the respectiveleak-barrier cuffs 7.

[0023] The end flap 8 of the rear waist region 22 is provided with anelastic member 10 associated with a waist-opening which comprises aplurality of elastic elements being stretchable in the transversedirection and secured under tension to this end flap 8. In the crotchregion 21, the side flaps 9 are provided with elastic members 11associated with leg-openings which comprises a plurality of elasticelements being stretchable and secured under tension to each of the sideflaps 9.

[0024] The plate-like member 6 is shaped in a substantially planarrectangle which is longer in the transverse direction and has inner andouter surfaces 6 a, 6 b. The plate-like member 6 lies between the end 4a of the core 4 and the elastic member 10 associated with thewaist-opening so as to extend along the end flap 8 of the rear waistregion 22 in the transverse direction. The plate-like member 6 isdisposed between the top and backsheets 2, 3 and secured to these sheets2, 3 in state free from contractile effect of the elastic members in thelongitudinal direction as well as in the transverse direction as bestseen in FIG. 1.

[0025] The plate-like member 6 has transversely opposite side portions 6c lying adjacent the respective side flaps 9 and an intermediate portion6 d extending between these side portions 6 c. The plate-like member 6is made of foamable polyethylene and has stiffness higher than that ofthe end flaps.

[0026] The leak-barrier cuffs 7 are provided on the respective sideflaps 9 and extend in the longitudinal direction. These leak-barriercuffs 7 respectively have fixed side edge portions 7 a extending in thelongitudinal direction in the vicinity of the side edges 4 b of the core4, free side edge portions 7 b normally biased to rise on the topsheet 2and fixed end portions 7 c collapsed inwardly of the diaper 1A in thetransverse direction. The leak-barrier cuffs 7 further have outermostside portions 7 d extending outwardly beyond the fixed side edgeportions 7 a in the transverse direction of the diaper 1A. The fixedside edge portions 7 a are joined bonded to the side edge portion 2 b ofthe topsheet 2 forming the respective side flaps 9. The fixed endportions 7 c are joined bonded to the end portion 2 a of the topsheet 2forming the respective end flaps 8. Elastic members 12 which arestretchable in the longitudinal direction are bonded under tension tothe free side edge portions 7 b and covered with parts of the respectivefree side edge portions 7 b.

[0027] The side flap 9 of the rear waist region 22 is provided with apair of tape fasteners 13 extending inward in the transverse direction.The tape fasteners 13 respectively have proximal end portions 13 adisposed between the side edge portions 3 b of the backsheet 3 and theoutermost side portions of the respective leak-barrier cuffs 7 andjoined to these sheets 3, 7. Free end portions 13 b of the respectivetape fasteners 13 are coated with pressure-sensitive adhesive 15. Thesefree end portions 13 b of the tape fasteners 13 are releasably fixed torelease film strips 16 which are made of plastic material and joined tothe outermost side edge portions 7 d of the respective leak-barriercuffs 7, by means of pressure-sensitive adhesive 15. The front waistregion 20 is provided with a rectangular target tape strip 14 made of aplastic film. This target tape strip 14 serves as a landing zone for thetape fasteners 13.

[0028] To wear the diaper 1A, the side flaps 9 in the rear waist region22 are placed upon outer sides of the respective side flaps 9 in thefront waist region 20 and the free end portions 13 b of the tapefasteners 13 are anchored to the target tape strip 14 by means ofpressure-sensitive adhesive 15 to connect the front waist region 20 withthe rear waist region 22. The plate-like member 6 is flexible and curvesto adapt a waist line of the wearer as the diaper 1A is worn.

[0029] With the front and rear waist regions 20, 22 connected to eachother, the diaper 1A defines a waist-opening 17 and a pair ofleg-openings 18 as seen in FIG. 2. The diaper 1A curves in thelongitudinal direction with the topsheet 2 inside and the free side edgeportions 7 b of the respective leak-barrier cuffs 7 rise on the topsheet2 as the elastic members 12 contract.

[0030] With the diaper 1A according to this invention, the plate-likemember 6 having stiffness higher than that of the end flap 8 is attachedto this end flap 8 so that the movement of the end flap 8 may berestrained by the plate-like member 6. Even if the contraction of theelastic member 10 associated with the waist-opening tends to shrink theend flap 8 and/or the movement of the wearer of the diaper 1A tends todistort the end flap 8, such a behavior of the end flap 8 is restrainedby the plate-like member 6. In this way, the diaper 1A according to thisinvention alleviates or eliminates a possibility that the end flap 8might shrink and a clearance might be generated between a region Z ofthe end flap 8 in which the plate-like member 6 is attached thereto (asindicated by an imaginary line) and the wearer's skin.

[0031] The plate-like member 6 preferably has stiffness of about 0.5mN·cm˜150 mN·cm as measured by the Gurley Stiffness Test. With thestiffness of the plate-like member 6 lower than about 0.5 mN·cm, itwould be impossible for the plate-like member 6 to restrain thepossibility of shrinkage and/or distortion occurring in the end flap 8.With the stiffness of the plate-like member 6 exceeding about 150 mN·cm,the region Z of the end flap 8 would have excessively high stiffnesscreating a feeling of discomfort against the wearer of the diaper 1A.

[0032] The end flaps 8 and the side flaps 9 preferably have stiffness ofabout 0.2 mN·cm˜1.0 mN·cm to maintain a desired flexibility of theseflaps 8, 9. Such values of stiffness were measured according toJIS(Japanese Industrial Standards) L 1096 (6.20.1).

[0033]FIG. 4 is a sectional view taken along a line B-B in FIG. 2 andFIG. 5 is a sectional view taken along a line C-C in FIG. 2. As seen inFIG. 4, the end flap 8 is formed by the end portions 2 a, 3 a of thetop- and backsheets 2, 3 extending outward beyond the longitudinal end 4a of the core 4 in the longitudinal direction and placed up and joinedto each other. The elastic member 10 associated with the waist-openingis disposed between these end portions 2 a, 3 a and joined to these endportions 2 a, 3 a.

[0034] In the side flaps 9, the side edge portions 2 b of the topsheet 2extending outward slightly beyond the side edges 4 b of the core 4 inthe transverse direction and the side edge portions 3 b of the backsheet3 as well as the outermost side edge portions 7 d of the leak-barriercuffs 7 further extend outward beyond the side edge portions 2 b of thetopsheet 2. The side edge portions 2 b are disposed between the sideedge portions 3 b and the outermost side edge portions 7 d and bonded tothese side edge portions 3 b and outermost side edge portions 7 d. Theside edge portions 3 b and the outermost side edge portions 7 d areplaced upon and bonded one to another. The elastic members 11 associatedwith the leg-openings are disposed between the side edge portions 3 band the outermost side edge portions 7 d of the respective leak-barriercuffs 7 and bonded to these side edge portions 3 b and the outermostside edge portions 7 d.

[0035]FIG. 6 is a view similar to FIG. 1 but showing a disposable diaper1B according to an alternative embodiment of this invention and FIG. 7is a sectional view taken along a line D-D in FIG. 6. The diaper 1Bshown by FIG. 6 is distinguished from the diaper 1A shown by FIG. 1 inan arrangement as follows. The inner surface 6 a of the plate-likemember 6 curves away from the wearer's skin so as to describe circulararcs between its transversely opposite end portions 6 c and theintermediate portion 6 d which curves, in turn, to be convex toward thewearer's skin.

[0036] With the diaper 1B worn, the transversely opposite end portions 6c of the plate-like member 6 follow bulges on the wearer's back in thevicinity of the ilia and the intermediate portion 6 d of the plate-likemember 6 follows a depression on the wearer's back in the vicinity ofthe lumbar. Consequently, the inner surface 6 a of the plate-like member6 comes in close contact with the wearer's skin.

[0037] With this diaper 1B also, the plate-like member 6 restrains thepossibility that the end flap 8 might shrink due to contraction of theelastic member 10 associated with the waist-opening and/or the end flap8 might be distorted due to the wearer' movement. In this way, thepossibility that the end flap 8 might shrink is alleviated and theanxiety that a clearance might be generated between the region Z of theend flap 8 and the wearer's skin is eliminated.

[0038] The topsheet 2 may be formed of a hydrophilic fibrous nonwovenfabric or a porous plastic film. The backsheet 3 may be formed of ahydrophobic fibrous nonwoven fabric or a liquid-impervious plastic film.The leak-barrier cuffs 7 may be formed of a hydrophobic fibrous nonwovenfabric.

[0039] It is also possible to form the backsheet 3 and the leak-barriercuffs 7 by a composite nonwoven fabric consisting of a melt blownfibrous nonwoven fabric having high water-resistance and two layers of aspun bond fibrous nonwoven fabric having high strength and flexibility.

[0040] The nonwoven fabric may be selected from a group including spunlace-, needle punch-, melt blown-, thermal bond-, spun bond-, chemicalbond- and air through-nonwoven fabrics. The component fibers of thenonwoven fabric may be selected from a group including polyolefine,polyester and polyamide fibers, and polyethylene/polypropylene orpolyethylene/polyester core-sheath-type or side-by-side type conjugatedfibers.

[0041] The core 4 is formed of a mixture of fluff pulp, high absorptionpolymer particles and thermoplastic synthetic resin fibers compressed toa desired thickness. The high absorption polymer may be selected from agroup including starch- and cellulose-based polymer and syntheticpolymer.

[0042] It is also possible to attach the plate-like member 6 to the endflap 8 in the front waist region 20. The plate-like member 6 may beformed not only of a formable polyethylene sheet but also of a flexibleand substantially non-stretchable plastic sheet or a mat-like sheetconsisting of a plurality of non-stretchable fibrous nonwoven fabriclayers. The plate-like member 6 is not limited to that of a rectangularshape and may be in the other optional shape such as transversely longerellipse or trapezoid.

[0043] Joining of the top- and backsheets 2, 3 to each other, fixing ofthe plate-like member 6 and the leak-barrier cuffs 7, joining of thecore 4 and attachment of the elastic members 10, 11, 12 may be carriedout using hot melt adhesive or heat welding technique such asheat-sealing or sonic sealing.

[0044] This invention is applicable to, in addition to the open-typediaper 1A, 1B, pants-type diaper having the front and rear waist regionspreviously connected to each other.

[0045] The disposable diaper according to this invention is primarilycharacterized by the plate-like member attached to the end flap at leastin the rear waist region and extending in the transverse direction. Thisplate-like member serves to restrain or eliminate an anxiety that theend flap might shrink due to contraction of the elastic memberassociated with the waist-opening and the end flap might be distorteddue to the wearer's movement. In this way, the possibility that the endflap might shrink can be alleviated and the apprehension that aclearance might be generated between the region of the end flap in whichthe plate-like member is attached to the end flap and the wearer's skinis eliminated.

[0046] In the case of the embodiment according to which the innersurface of the plate-like member curves away from the wearer's skin soas to describe circular arcs between its transversely opposite endportions and the intermediate portion which curves, in turn, to beconvex toward the wearer's skin, not only shrinkage and distortion ofthe end flap are restrained by the plate-like member but also fitness ofthe plate-like member to the wearer's skin can be improved in comparisonwith the case in which the inner surface of the plate-like member issubstantially flat. This is because the inner surface of the plate-likemember well follows contouring of the waist line on the wearer's back.

What is claimed is:
 1. A disposable diaper comprising a liquid-pervioustopsheet, a liquid-impervious backsheet and a liquid-absorbent coredisposed between these sheets so as to define, a front waist region, arear waist region and a crotch region extending between these waistregions, and a pair of end flaps extending outward in a longitudinaldirection of said diaper from longitudinally opposite ends of said corelying in said front and rear waist regions: said disposable diaperfurther comprising a plate-like member which is flexible andsubstantially non-stretchable and is attached to an end flap at least ina rear waist region to extend in a transverse direction and hasstiffness higher than that of the end flap.
 2. The disposable diaperaccording to claim 1, wherein an elastic member associated with awaist-opening being stretchable in said transverse direction is securedunder tension to said end flap at least in said rear waist region andsaid plate-like member lies between said end of said core and saidelastic member associated with the waist-opening.
 3. The disposablediaper according to claim 1, wherein said plate-like member hastransversely opposite side portions and an intermediate portionextending between said transversely opposite side portions and whereininner surface of said plate-like member facing a wearer's skin curvesfrom said transversely opposite side portions toward said intermediateportion so as to describe circular arcs going far off from the wearer'sskin.
 4. The disposable diaper according to claim 3, wherein saidintermediate portion of said plate-like member is formed to be convextoward the wearer's skin.
 5. The diaper according to claim 1, whereinsaid plate-like member is made of foamable polyethylene and hasstiffness of about 0.5 mN·cm˜150 mN·cm as measured by Gurley's StiffnessTest.